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Troß J, Carter-Fenk K, Cole-Filipiak NC, Schrader P, Word M, McCaslin LM, Head-Gordon M, Ramasesha K. Excited-State Dynamics during Primary C-I Homolysis in Acetyl Iodide Revealed by Ultrafast Core-Level Spectroscopy. J Phys Chem A 2023; 127:4103-4114. [PMID: 37103479 DOI: 10.1021/acs.jpca.3c01414] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/28/2023]
Abstract
In typical carbonyl-containing molecules, bond dissociation events follow initial excitation to nπC═O* states. However, in acetyl iodide, the iodine atom gives rise to electronic states with mixed nπC═O* and nσC-I* character, leading to complex excited-state dynamics, ultimately resulting in dissociation. Using ultrafast extreme ultraviolet (XUV) transient absorption spectroscopy and quantum chemical calculations, we present an investigation of the primary photodissociation dynamics of acetyl iodide via time-resolved spectroscopy of core-to-valence transitions of the I atom after 266 nm excitation. The probed I 4d-to-valence transitions show features that evolve on sub-100-fs time scales, reporting on excited-state wavepacket evolution during dissociation. These features subsequently evolve to yield spectral signatures corresponding to free iodine atoms in their spin-orbit ground and excited states with a branching ratio of 1.1:1 following dissociation of the C-I bond. Calculations of the valence excitation spectrum via equation-of-motion coupled cluster with single and double substitutions (EOM-CCSD) show that initial excited states are of spin-mixed character. From the initially pumped spin-mixed state, we use a combination of time-dependent density functional theory (TDDFT)-driven nonadiabatic ab initio molecular dynamics and EOM-CCSD calculations of the N4,5 edge to reveal a sharp inflection point in the transient XUV signal that corresponds to rapid C-I homolysis. By examining the molecular orbitals involved in the core-level excitations at and around this inflection point, we are able to piece together a detailed picture of C-I bond photolysis in which d → σ* transitions give way to d → p excitations as the bond dissociates. We also report theoretical predictions of short-lived, weak 4d → 5d transitions in acetyl iodide, validated by weak bleaching in the experimental transient XUV spectra. This joint experimental-theoretical effort has thus unraveled the detailed electronic structure and dynamics of a strongly spin-orbit coupled system.
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Affiliation(s)
- Jan Troß
- Combustion Research Facility, Sandia National Laboratories, Livermore, California 94550, United States
| | - Kevin Carter-Fenk
- Kenneth S. Pitzer Center for Theoretical Chemistry, Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Neil C Cole-Filipiak
- Combustion Research Facility, Sandia National Laboratories, Livermore, California 94550, United States
| | - Paul Schrader
- Combustion Research Facility, Sandia National Laboratories, Livermore, California 94550, United States
| | - Mi'Kayla Word
- Combustion Research Facility, Sandia National Laboratories, Livermore, California 94550, United States
| | - Laura M McCaslin
- Combustion Research Facility, Sandia National Laboratories, Livermore, California 94550, United States
| | - Martin Head-Gordon
- Kenneth S. Pitzer Center for Theoretical Chemistry, Department of Chemistry, University of California, Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Krupa Ramasesha
- Combustion Research Facility, Sandia National Laboratories, Livermore, California 94550, United States
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Forbes R, Neville SP, Larsen MAB, Röder A, Boguslavskiy AE, Lausten R, Schuurman MS, Stolow A. Vacuum Ultraviolet Excited State Dynamics of the Smallest Ketone: Acetone. J Phys Chem Lett 2021; 12:8541-8547. [PMID: 34464141 DOI: 10.1021/acs.jpclett.1c02612] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
We combined tunable vacuum-ultraviolet time-resolved photoelectron spectroscopy (VUV-TRPES) with high-level quantum dynamics simulations to disentangle multistate Rydberg-valence dynamics in acetone. A femtosecond 8.09 eV pump pulse was tuned to the sharp origin of the A1(n3dyz) band. The ensuing dynamics were tracked with a femtosecond 6.18 eV probe pulse, permitting TRPES of multiple excited Rydberg and valence states. Quantum dynamics simulations reveal coherent multistate Rydberg-valence dynamics, precluding simple kinetic modeling of the TRPES spectrum. Unambiguous assignment of all involved Rydberg states was enabled via the simulation of their photoelectron spectra. The A1(ππ*) state, although strongly participating, is likely undetectable with probe photon energies ≤8 eV and a key intermediate, the A2(nπ*) state, is detected here for the first time. Our dynamics modeling rationalizes the temporal behavior of all photoelectron transients, allowing us to propose a mechanism for VUV-excited dynamics in acetone which confers a key role to the A2(nπ*) state.
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Affiliation(s)
- Ruaridh Forbes
- Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT, U.K
- Department of Physics, University of Ottawa, 150 Louis Pasteur Pvt, Ottawa, ON K1N 6N5, Canada
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Simon P Neville
- National Research Council of Canada, Ottawa, ON K1A 0R6, Canada
| | - Martin A B Larsen
- Department of Chemistry, University of Copenhagen, 2100 Copenhagen ø, Denmark
| | - Anja Röder
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, 150 Louis Pasteur Pvt, Ottawa, ON K1N 6N5, Canada
| | - Andrey E Boguslavskiy
- Department of Physics, University of Ottawa, 150 Louis Pasteur Pvt, Ottawa, ON K1N 6N5, Canada
| | - Rune Lausten
- National Research Council of Canada, Ottawa, ON K1A 0R6, Canada
| | - Michael S Schuurman
- National Research Council of Canada, Ottawa, ON K1A 0R6, Canada
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, 150 Louis Pasteur Pvt, Ottawa, ON K1N 6N5, Canada
| | - Albert Stolow
- Department of Physics, University of Ottawa, 150 Louis Pasteur Pvt, Ottawa, ON K1N 6N5, Canada
- National Research Council of Canada, Ottawa, ON K1A 0R6, Canada
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, 150 Louis Pasteur Pvt, Ottawa, ON K1N 6N5, Canada
- Joint Centre for Extreme Photonics, University of Ottawa - National Research Council, Ottawa, ON K1N 5A2, Canada
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Vlasov S, Ponomarev A. Signs of keto-enol tautomerism in acetone radiolysis. Radiat Phys Chem Oxf Engl 1993 2021. [DOI: 10.1016/j.radphyschem.2021.109460] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Heim P, Mai S, Thaler B, Cesnik S, Avagliano D, Bella-Velidou D, Ernst WE, González L, Koch M. Revealing Ultrafast Population Transfer between Nearly Degenerate Electronic States. J Phys Chem Lett 2020; 11:1443-1449. [PMID: 31918552 PMCID: PMC7052817 DOI: 10.1021/acs.jpclett.9b03462] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Accepted: 01/10/2020] [Indexed: 06/10/2023]
Abstract
The response of a molecule to photoexcitation is governed by the coupling of its electronic states. However, if the energetic spacing between the electronically excited states at the Franck-Condon window becomes sufficiently small, it is infeasible to selectively excite and monitor individual states with conventional time-resolved spectroscopy, preventing insight into the energy transfer and relaxation dynamics of the molecule. Here, we demonstrate how the combination of time-resolved spectroscopy and extensive surface hopping dynamics simulations with a global fit approach on individually excited ensembles overcomes this limitation and resolves the dynamics in the n3p Rydberg states in acetone. Photoelectron transients of the three closely spaced states n3px, n3py, and n3pz are used to validate the theoretical results, which in turn allow retrieving a comprehensive kinetic model describing the mutual interactions of these states for the first time.
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Affiliation(s)
- Pascal Heim
- Institute
of Experimental Physics, Graz University
of Technology, Petersgasse 16, A-8010 Graz, Austria
| | - Sebastian Mai
- Institute
of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Str. 17, A-1090 Vienna, Austria
| | - Bernhard Thaler
- Institute
of Experimental Physics, Graz University
of Technology, Petersgasse 16, A-8010 Graz, Austria
| | - Stefan Cesnik
- Institute
of Experimental Physics, Graz University
of Technology, Petersgasse 16, A-8010 Graz, Austria
| | - Davide Avagliano
- Institute
of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Str. 17, A-1090 Vienna, Austria
| | - Dimitra Bella-Velidou
- Institute
of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Str. 17, A-1090 Vienna, Austria
| | - Wolfgang E. Ernst
- Institute
of Experimental Physics, Graz University
of Technology, Petersgasse 16, A-8010 Graz, Austria
| | - Leticia González
- Institute
of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Str. 17, A-1090 Vienna, Austria
| | - Markus Koch
- Institute
of Experimental Physics, Graz University
of Technology, Petersgasse 16, A-8010 Graz, Austria
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